Beta-alanine hydrazides



United States Patent O 3,456,006 B-ALANINE HYDRAZIDES David Aelony, Minneapolis, Minn., assignor to General Mills, Inc., a corporation of Delaware No Drawing. Filed Jan. 17, 1967, Ser. No. 609,747 Int. Cl. C07c 103/20, 103/10; C08g 51/04 US. Cl. 260-558 4 Claims ABSTRACT OF THE DISCLOSURE Compounds of the formula and compositions comprising such hydrazides and epoxy resins. A representative compound is prepared by condensing dimethylamine with ethyl acrylate and then reacting the resulting adduct with hydrazine. Such hydrazides react rapidly with epoxy resins at elevated temperatures and yet are used to prepare mixtures or B-stage resins with the epoxy resins which are relatively stable at room temperature.

The present invention relates to certain novel hydrazides and the use thereof as curing agents for epoxy resins. More particularly, it relates to certain amino substituted hydrazides which are especially useful as curing agents for epoxy resins.

Epoxy resins are known to produce a number of valuable products and, particularly in the coating arts, the epoxy resins are known to produce infusible, insoluble coatings or films which when properly cured exhibit desirable properties such as toughness, thermal stability and the like. The known curing agents for such epoxy resins, however, have been found to leave something to be desired. For example, the common aliphatic polyamines react rapidly at room temperature and at elevated temperatures with epoxy resins. They therefore possess poor storage stability. In addition, since most of the compounds of this class are liquids, they are difficult to utilize in powder systems. Other agents that have been utilized are the aminotriazines, anhydrides and aromatic diamines. These compounds, however, give moderate rates of reaction with epoxy resins at low and high temperatures and consequently cure rates are quite slow.

The hydrazides of the present invention have the advantage of being compatible with epoxy resins to form compositions which are stable at room temperature. They can also be readily and easily reacted at elevated temperatures with epoxy resins and the reaction can be termi nated prior to completion to provide relatively stable, homogeneous B-stage resins of high utility. Such systems can be finely divided to provide stable, homogeneous powders for use in coating a variety of substrates by such methods as spraying and fluidization thereof. The admixtures or B-stage resins, even though stable at ambient room temperatures, are rapidly cured when heated to elevated temperatures.

It is, therefore, an object of the instant invention to provide novel amino substituted hydrazides.

Another object of the invention is to provide novel hardenable epoxy resin compositions.

Still another object of the invention is to provide novel partially cured, hardenable epoxy resin compositions.

A further object of the invention is to provide novel infusible, insoluble epoxy resin products.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof.

ice;

In general, the instant invention consists in new substances or materials that are hydrazides of adducts having the formula where R is an aliphatic radical of 1 to about 24 carbon atoms, or an aryl group which may or may not be substituted such as with aliphatic groups to give an alkaryl group, or an aralkyl group wherein the aryl group may or may not be substituted such as with additional aliphatic groups; R is a straight or branched chain alkylene radical of from 2. to about 11 carbon atoms; and R" is an aliphatic, preferably alkyl, group of 1 to about 4 carbon atoms. It is preferred that R and R are unsubstituted hydrocarbon radicals. The two R radicals may be the same or different. The present invention further consists in hardenable compositions prepared from such hydr-azides and epoxy resins and in infusible, insoluble resinous products prepared from such hardenable compositions.

One preferred method of preparing the adducts used to produce the hydrazides of the present invention is to condense a secondary amine and a lower aliphatic ester of an alpha, beta unsaturated acid. Representative aliphatic secondary amines used in such condensation reaction are dimethyl amine, diethyl amine, dipropyl amine, dibutyl amine, dipentyl amine, dihexyl amine, dicyclohexyl amine, diheptyl amine, dioctyl amine, dinonyl amine, didecyl amine, diundecyl amine, didodecyl amine, dihexadecyl amine, dioctadecyl amine, dihexenyl amine, diheptenyl amine, dioctenyl amine, dihexadecenyl amine, dioctadecenyl amine, distearyl amine, dioleyl amine, dioctynyl amine, dioctadecynyl amine and the like. Said amines may be branched chained amines. Representative side chain substituents are methyl, ethyl, propyl, butyl, pentyl, hexyl, hexenyl, heptyl, heptenyl, heptynyl, octyl, octenyl, decyl and the like. The amines may have one or more side chains, may be mono-, dior tri-unsaturated, and may be substituted with inert or non-interfering groups such as chlorine, nitro and the like.

Representative aryl secondary amines are diphenylamine and the substituted derivatives thereof, including the dialkaryl amines. Such amines can be represented by the formula:

where Ar is the cyclic moiety, R" is a substituent such as methyl, ethyl, propyl, butyl, pentyl, pentenyl, hexenyl, hexyl, 2-ethyl hexyl, hexynyl, octyl, decyl, decenyl, decynyl, and the like. Either the cyclic moiety or the substituent may contain inert or non-interfering groups such as halogen, nitro, and the like. The aryl or alkaryl radicals preferably contain from about 6 to 40 carbon atoms and it is preferred that the cyclic moiety contains no more than about 2 substituents. It is even more preferred that the cyclic moiety contains 1 or less substituents. x in the above formula is an integer representing the number of aliphatic substituents on the cyclic moiety. A representative aralkyl secondary amine is dibenzyl amine. Such amines can be represented by the formula radical which may be branched and preferably contains from about 1 to 10 carbon atoms. Either the cyclic moiety, R" or the substituent R may contain inert or non-interfering groups. The aralkyl radicals preferably contain from 7 to 40 carbon atoms and it is also preferred that the cyclic moiety contains less than two aliphatic substituents.

The preferred amines are the straight chain saturated aliphatic secondary amines. The preferred esters to be condensed with the said secondary amines are the esters of D ri-unsaturated acids such as the lower aliphatic esters of acrylic acid, methacrylic acid and crotonic acid. Such condensation reaction can be illustrated as follows:

di-n-butyl amine methyl methacrylate N CHaCH i 0 CH3 C H3 (C H2) 3 C Ha The condensation of the secondary amine and the ester is preferably carried out at temperatures of from about to 120 C. At room temperature or lower the reaction requires a somewhat extended period of time. It is also preferred that such reaction be carried out in the presence of a lower aliphatic alcohol or 1,4-dioxane, the same accelerating the reaction. Representative alcohols are methanol, ethanol, propanol, isopropanol, secondary butanols and tertiary butanol. Preferably quantities of about 2 to 25% by weight based on the total weight of the reactants are employed.

Another method of preparing the adducts used to produce the hydrazides of my invention is by reductive amination of esters of aldehydic acids. This reaction can be illustrated as follows:

The resulting product is then hydrogenated to yield NCHzR"'C o R" The condensation and hydrogenation are preferably carried out in a single step. R""' represents a divalent straight chain or branched chain alkylene group which preferably contains from 2 to about 10 carbon atoms. Said group may contain inert or noninterfering substituents.

Representative aldehydic esters for use in the above method are propyl succinaldehydate, isopropyl succinaldehydrate, sec.-butyl succinaldehyde, terL-butyl succinaldehydate the corresponding propylisopropyl-, sec.-butyl-, and tert.-butyl glutaraldehydates, adipaldehydates, pim'elaldehydates, and sebacaldehydates and the corresponding esters of fi-methylglutaraldehydic acid, 'yq-dimethylglutar- 'aldehydic acid, and the like. The useful amines are those described hereinabove. This reaction is preferably carried out at from 115 to 160 C., at a pressure of from 1 to 1000 atmospheres and in the presence of hydrogen and a hydrogenation catalyst.

The hydrazides of the present invention have the formula:

where R and R have the meanings set forth above. They are prepared by reacting hydrazine with the above- 4 described adducts. This reaction can be illustrated as follows:

NCHQCHgiBOCHt (NHz-NHz) CHKCH,

NCHzOHzNH-NH: CHaOH The reaction is preferably carried out using aqueous hydrazine of high concentrationi.e. 97% hydrazine by weight. It is also preferred to carry out the reaction in the presence of a lower aliphatic alcohol such as methanol. While the reaction can be completed at room temperature, higher temperatures on the order of to 110 C. are preferred. Reflux conditions are especially preferred.

The following specific description illustrates the preparation of the hydrazides of the present invention.

EXAMPLE 1 (a) Preparation of ethyl fi-dimethylaminopropionate One hundred grams of dimethylamine were dissolved in one pint of absolute ethyl alcohol. The resulting solution was cooled to 7 C. and then 222.2 g. ethyl acrylate was added with stirring (temperature rose to 19 C.). Stirring was continued at room temperature for 1% hours and then the reaction temperature was graduallyincreased to reflux conditions in one hour. The reaction mixture was refluxed for three hours, allowed to stand overnight and then stripped and fractionated in vacuum. There was obtained 295 g. of ethyl fl-dimethylaminopropionate having the formula:

CH fi NGHaCHzC-OOHgCH;

(b) Preparation of fl-dimethylaminopropionhydrazide Two hundred ninety grams of the ethyl ii -dimethylaminopropionate as prepared in (a), ml. of 97% hydrazine and 100 ml. methanol were combined and refluxed overnight. The solvent and excess hydrazine were then removed by evaporation. There was obtained 256 g. of hydrazide having an amine number of 825. The [3- dimethylaminopropionhydrazide had the formula:

OH: H

NCHaCHzCNH-NH:

The following hydrazides are prepared in a similar manner from the reactants indicated in parentheses.

EXAMPLE 2.-,B-didodecylaminopropionhydrazide (didodecylamine, ethylacrylate, hydrazine) G N mu NCH2CHzCNH-NH1 :t( t)u EXAMPLE 3.[3-Dioctadecylaminopropionhydrazide (dioctadecylamine, ethylacrylate, hydrazine) Hs( 2)11 H NOHzOHzCNH-NHa EXAMPLE 4.- 3-Dibenzylaminopropionhydrazide (dibenzylamine, ethylacrylate, hydrazine) As indicated above the hydrazides of the present invention are particularly useful as curing agents for epoxy resins. Any epoxy resin can be used in the present invention. Suitable resins include the reaction products of polyhydric phenols with polyfunctional halohydrins. Typical polyhydric phenols useful in the preparation of such resins include resorcinol and various bisphenols resulting from the condensation of phenol with aldehydes and ketones such as formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, and the like. A typical epoxy resin of this type is the reaction product of epichlorohydrin and 2,2-bis (p-hydroxyphenyl)pr0pane (Bisphenol A), the resin having the following theoretical structural formula:

0 CH3 OH CH 0 H...4:0H ofiaorgto CH. tH CH.o)@t ..male...

where n is 0 or an integer up to 10. Generally speaking, n will usually be no greater than 3 or 4, and may be 1 or less. However, other types of epoxy resins may be employed.

Another of such epoxy resins are those which are the reaction product of epichlorohydrin and bis(p-hydroxyphenyl) sulfone. Still another group of epoxy compounds which may be employed are the glycidyl esters of polymeric fat acids. These glycidyl esters are obtained by reacting the polymeric fat acids with polyfunctional halohydrins such as epichlorohydrins. In addition, the glycidyl esters are also commercially available epoxide materials. As the polymeric fat acids are composed largely of dimeric acids, the glycidyl esters thereof may be represented by the following theoretical, idealized formula:

where -R is the divalent hydrocarbon radical of dimerized unsaturated fatty acids.

The polymeric fat acids are well known materials, commercially available, which are the products prepared from the polymerization of unsaturated fatty acids to provide a mixture of dibasic and higher polymeric fat acids. The polymeric fat acids are those resulting from the polymerization of the drying or semi-drying oils or the free acids or the simple aliphatic alcohol esters of such acids. Suitable drying or semi-drying oils include soybean, linseed, tung, perilla, oiticia, cottonseed, corn, sunflower, safflower, dehydrated castor oil, and the like. The term polymeric fat acids, as used herein and as understood in the art, is intended to include the polymerized mixture of acids which usually contain a predominant portion of dimer acids, a small quantity of trimer and higher polymeric fat acids and some residual monomers.

In general, the most readily available naturally occurring polyunsaturated acid available in large quantities is linoleic. Accordingly, it should be appreciated that polymeric fat acids will as a practical matter result from fatty acid mixtures that contain a preponderance of linoleic acid and will thus generally be composed largely of dimerized linoleic acid. However, polymerized fatty acids may be prepared from the naturally occurring fatty acids having from 6 to 22 carbon atoms. Illustrative thereof are oleic, linolenic, palmitoleic, and the like. Glycidyl esters of other polybasic acids, such as phthalic and sebacic acids, may be employed.

Other types of epoxy resins which may be used with the hydrazides of the present invention and which are commercially available epoxy materials are the polyrohydrin and the tetraphenol may be represented by the following theoretical structural formula:

Where R is selected from the group consisting of hydrogen and alkyl groups having up to 18 carbon atoms, and n is an integer of from 1 to 10. Generally, n will be an integer in excess of 1 to about 5.

In general, these resins are obtained by glycidification of the well-known novolac resins. The novolac resins, as is known in the art, are produced by condensing the phenol with an aldehyde in the presence of an acid catalyst. Although novolac resins from other aldehydes such as, for example, acetaldehyde, chloral, butyraldehyde, furfural, and the like, may also be used. The alkyl group, if present, may have a straight or a branched chain. Illustrative of the alkylphenol from which the novolac resins may be derived are cresol, butylphenol, tertiary butylphenol,

tertiary amylphenol, hexylphenol, 2 ethylhexylphenol,

nonylphenol, decylphenol, dodecylphenol, and the like. It is generally preferred, but not essential, that the alkyl substituent be linked to the para carbon atom of the parent phenolic nucleus. However, novolac resins in which the alkyl group is in the ortho psoition have been prepared.

The glycidized novolac resin is formed in the wellknown manner by adding the novolac resins to the epichlorohydrin and then adding an alkali metal hydroxide to the mixture so as to effect the desired condensation reaction.

In addition, other epoxy resins which may be used with the hydrazides of the present invention are epoxidized olefins, such as epoxidized polybutadiene and epoxidized cyclohexenes, and the diglycidyl ethers of the polyalkylene glycols. These latter ethers are readily available commercially and may be represented by the following theoretical, idealized formula:

where R is an alkylene radical having from 2 carbon atoms and n is an integer of from about 1 to about 50. R is preferably ethylene or propylene .or mixtures thereof and n is preferably about 3 to about 10. It is understood that n represents an average figure since the ethers are often prepared from a mixture of glycolsi.e., tripropylene glycol, tetrapropylene glycol, and the like. Said epoxy resins may be prepared in the manner set forth in US. Patent 2,923,696.

In general, the epoxy resins may be described as those having terminal epoxide groups, or at least as having more than one epoxide group per mole.

In addition, the epoxy resins may be characterized further by reference to their epoxy equivalent weight, the epoxy equivalent weight of pure epoxy resin being the means molecular weight of the resins divided by the mean number of epoxy radicals per molecule, or in any case, the number of grams of epoxy equivalent to one epoxy group or one gram equivalent of epoxide. The epoxy resinous materials employed in this invention have epoxy equivalent weights of from about 140 to about 2000.

The hydrazides of the present invention are used in an amount suflicient to cure the epoxy resin to an insoluble and infusible polymer. Preferably, the hydrazides are used in ratios by weight curing agent to epoxy resin of from about 1:99 to 75:25.

As indicated previously, the present invention consists of the hydrazides, curable compositions of the hydrazides and epoxy resins, partially cured compositions of the hydrazides and epoxy resins and the ultimately prepared insoluble and infusible polymers prepared from the hydrazides and epoxy resins. The curable compositions may be prepared simply by admixing the epoxy resin and the hydrazide in the desired proportions. Such compositions are stable for extended periods of time at ambient room temperature and yet can be cured rapidly by heating to elevated temperatures. They may or may not be homogeneous.

The partially cured or B-stage resins may be prepared by admixing the hydrazide and epoxy resin in the desired proportions, heating the reaction mixture to temperatures of about 30 C. to about 250 C., preferably 35 C. to 200 C., for a short period of time and terminating the reaction by cooling. By B-stage resin is meant a partially reacted product which will undergo little or no physical change during extended storage at ambient room temperatures and in which the reactants are homogeneously compatible in a one component, stable compound ready for final curing at elevated temperatures. In general, a B-stage resin will exist when the reaction is from about 5 to 90% complete.

The cured compositions of the present invention are prepared by heating the curbale compositions or the partially cured compositions at elevated temperatures for a suificient length of time to form insoluble and infusible polymers. Preferred heating temperatures are from about 300 to 450 F.

The hydrazide-epoxy resin compositions of my invention can also contain conventional additives such as pigments, fillers, flow control and anti-caking agents, accelerators, solvents and the like. In a preferred embodiment, the curable compositions or partially cured compositions are finely divided to form powders which find particular use in the coating of various substrates. Such powders give good edge coverage of sharp corners and thin panel edges. The B-stage powders are homogeneous,

one-component materials which are stable at ambient room temperatures and yet can be rapidly cured at elevated temperatures. The same can be applied by the use of spray techniques or by forming a fluidized bed thereof. Normally the substrate to be coated is heated prior to being sprayed with the powder or being dipped into the the fluidized bed. The powder then melts and coats the substrate. Subsequent curing, if necessary, can be in ovens heated to elevated temperatures. The powders of the present invention are especially valuable because of their quick cure characteristics.

The powders preferably contain flow control and anticaking agents. Examples of such agents include amorphous silicas', dehydrated silica gels, various natural silicates such as attapulgite and kaolin clays, amorphous alumina, talc, and finely divided calcium carbonate. The described agents are preferably used in an amount sufficient to improve the flowout of the powder on melting with heat and/or to prevent fusing or caking of the powder at moderately high temperatures, i.e. -125 F. Obviously, the amounts of said agents can vary considerably, depending on the particular agent used and the result desired. Generally, said agents will be used in amounts of about 2 to 50% by weight based on the weight of the epoxy resin and the hydrazide.

The hydrazide-epoxy resin compositions, and particularly the coating powders derived therefrom, may also contain colorants, pigments, or fillers. Examples of suitable pigments include titanium dioxide (white finish), lead chromate (yellow), light and medium chrome yellow, chrominum oxide (green), ultramarine blue, red iron oxide, and toluidine red. The amounts of said pigments can be varied widely to give different shades of different colors. Additionally, mixtures of different pigments may be used. Generally, said pigments are used in amounts of about 1 to 15% by weight based on the weight of the epoxy resin and hydrazide.

The hydrazide-epoxy resin compositions of this invention are useful not only in the coatings art but also in the preparation of laminates, moldings and the like. preferred epoxy resins to be used are the glycidyl ethers of polyhydric phenols such as Bisphenol A.

The following specific description illustrates the hydrazide-epoxy compositions of the present invention.

EXAMPLE A To 9.78 g. of epoxy resin (a condensation product of Bisphenol A and epichlorohydrin having an epoxy equivalent weight of about 177) was added 0.22 g. fi-dimethylaminopropionhydrazide as prepared in Example 1 above. No reaction of the epoxy and hydrazide was evident at room temperature. The mixture was slowly heated to 200 C. and upon reaching this temperature the reaction product (B-stage resin) was poured onto a Teflon sheet to cool. The cooled partially cured product was solid and homogeneous. Upon being subdivided and heated to 400 -F., it gelled instantly indicating its high utility. Thus a relatively stable coating powder can be prepared from the partially cured resin and the same can be fluidized and applied to a heated substrate. The resulting film on the substrate gels instantly and is rapidly cured.

EXAMPLES B-D Example A is repeated using the hydrazides of Examples 2-4. Essentially the same results are obtained.

It is to be understood that the invention is not to be limited to the exact details of operation or the exact compositions shown or described, as obvious modifications and equivalents will be apparent to those skilled in the art and the invention is to be limited only by the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The compound having the formula:

2. The compound having the formula:

C Ha(C 111) i H N C 112C 1120 NII=N ll;

3. The compound having the formula:

C H3 (C H2)17 4. The compound having the formula:

References Cited UNITED STATES PATENTS 3/1961 Nischk 260-558 OTHER REFERENCES Edwards et al.: J. Pharm. PharmacoL, 1964, vol. 16,

US. Cl. X.R. 

